Remediation of former sawmill, East Yorkshire

Remediation of former sawmill, East Yorkshire

Soil below the footprint of the former creosote shed was excavated to depths of between c.2.65m and c.3.30m below current ground levels. Initially it was anticipated the creosote contamination was perched on top of clay layer at a depth of c.1.80m, however during excavation it was evident that the contamination had in fact penetrated the clay through fissures to depths of up to c.3.00m. This clay layer also contained lenses/pockets of black and dark brown stained creosote impacted gravel. The area of creosote impacted soils extended laterally beyond the footprint of the former creosote shed, most significantly to the east.

The impacted spoil recovered from the excavation was stockpiled overnight on concrete and visqueen to the west prior to disposal off site. The area of the excavation was approximately 120m2 at the surface with battered sides resulting in a smaller base area.

Significant creosote contamination was noted to be present on and beyond the southern boundary of the site, although excavation had to be terminated due to the constraints of the site. It was recommended to the client at that stage, that barrier system (i.e. slurry trench or clay cut off wall) would be required to prevent contamination migrating back onto the site at a later date

In addition the soil below and adjacent to a former AST's were delineated and excavated. Based on visual and olfactory evidence an area of approximately 16.20m2 was recovered. The maximum depth penetration by the fuel/oil was c.0.90m below current ground levels, although the excavation was taken down to c.1.10m to ensure no further vertical migration had occurred. In total c.18m3 of impacted soil was removed from this location and placed directly into dedicated transportation (20 tonne wagons) before being taken to landfill along with the stockpiled materials removed from the creosote shed excavation the previous day.

Various photographs of the initial walkover, field observations, drilling and sampling works and remediation are below